Las Bellostas is not anywhere near
 any mayor road. It is probably best to start from Boltaña and take the
 road towards Lanave and the 
Puerto de Serrablo (A-1604). 
 After 11 km on this narrow and winding road there is a branch to the left towards Las Bellostas and 
Paúles de Sarsa. It is before the highest point of the Puerto at km-39.
 Follow this narrow road until you reach the village. At the entrance of the village turn right
 and once more right and you should reach the end of the metalled road in the lowest
 part of the village. Find the markers of the GR-1 and follow the trail to the West.
 The trail will cross a gravel road and from then on you should follow the road going down into the 
 valley of the 
Río Balces (or Isuala) where the mill is. It is
 a walk of about half an hour from the village.
Pallaruelo, in his book Los Molinos del Altoaragón (1994),
 has dedicated several pages to this striking construction and its waterworks.
Pictures: V.1995, 21.VII.2015, 4.X.2016